This invention relates to navigation and guidance of a follower aircraft such as an uninhabited air vehicle (UAV) relative to a leader aircraft and specifically to an aerial refueling and formation flying system for UAVs.
Aerial refueling and formation flying with an uninhabited air vehicle poses a unique flight control challenge because of the bandwidth of the control mechanism required and because it is desirable to implement a passive (non-RF emitting) positioning source.
With piloted aircraft aerial refueling, relative navigation for the rendezvous is accomplished with equipment such as TACAN and barometric altimeters. Fine navigation during connect, fueling, and disconnect is done visually by a pilot and a tanker boom operator. For the rendezvous phase, the major problem with TACAN is that it is not a low-observable waveform.
Uninhabited air vehicles require precise relative navigation capability to perform many mission functions such as formation flying and aerial refueling. In most situations GPS techniques suitably augmented with inertial data may suffice for UAV relative navigation. In a UAV aerial refueling system, coarse position reporting during rendezvous is sufficient. High accuracy is not required with standalone GPS positioning being adequate. For communications with the UAV a low-observable communications datalink is needed with a modest data rate. Precise, low-latency three-dimensional relative navigation is required throughout the entire capture/connect/fueling/disconnect process with the tanker boom operator having control over the UAV at close range.
High-accuracy relative positioning is required during capture and refueling or during formation flying of the UAV. A system is desired that offers the needed control bandwidth with a low observable datalink means.